On Wed, 19 Feb 2020, Klaus Doldinger wrote:
Am 19.02.20 um 11:02 schrieb Jonathan Wakely:
On Wed, 19 Feb 2020 at 07:53, Klaus Doldinger
<klaus.doldinger64@xxxxxxxxx> wrote:
The following was possible in v9:
template<auto N>
struct A {
constexpr auto size() const {
return N;
}
};
template<typename A>
void foo(const A& a) {
constexpr auto s = a.size();
}
int main() {
A<10> x1;
foo(x1);
}
In v10 this is rejected.
Looks like a bug?
Clang also rejects it.
No, I don't think so. The parameter a is not a constant expression, so
a.size() is not a constant expression, so can't be used to initialize
a constexpr variable.
Why not make size() static?
That would be weird.
If so, the follwing would be impossible:
std::array<int, 10> a;
std::array<int, a.size()> b;
You can still use decltype and tuple_size to access that information.
--
Marc Glisse
